BIPOLAR RADIOFREQUENCY CATHETER ABLATION CREATES CONFLUENT LESIONS ATA LARGER INTERELECTRODE SPACING THAN DOES UNIPOLAR ABLATION FROM 2 ELECTRODES IN THE PORCINE HEART

Aims Radiofrequency catheter ablation of atrial flutter and fibrillati on may be favoured by large, elongated lesions. We compared bipolar ab lation with unipolar ablation from one or two electrodes in the porcin e heart. Methods and Results In vitro, confluent lesions were reliably created by a 'dielectrode' catheter (energy delivered simultaneously tin parallel) from two 4 mm electrodes spaced I mm apart, towards an i ndifferent electrode), and a 'bipolar' catheter (energy delivered tin series) between two 4 mm electrodes spaced 5 mm apart). Sixteen anaest hetized pigs were randomized to standard unipolar (4), dielectrode (6) or bipolar (6) ablation. Two radiofrequency current deliveries of 30 s duration (70 degrees C) were administered to the inferior vena cava- tricuspid valve isthmus and two to the right atrial free wall in all a nimals. After 4 h, the lesions were examined macroscopically and histo logically. Mean (SD) endocardial lesion length x width x depth measure d 7.4 (2.4) x 5.4 (2.2) x 2.8 (0.8) mm in the standard unipolar mode, 10.2 (1.4)x 6.3 (0.7)x 3.3 (1.1) mm in the dielectrode mode and 14.0 ( 3.6) x 6.0 (1.7) x 3.8 (1.2) mm in the bipolar mode. Thus lesion lengt h increased significantly through the three groups (P < 0.001), while width and depth did not. Conclusion Both dielectrode and bipolar ablat ion were feasible in porcine right atrial ablation, and created longer lesions than the standard unipolar mode. By allowing a larger interel ectrode distance, bipolar ablation created the longest lesions and may be favourable when linear lesions are necessary.